Based on a current trend toward energy saving, attention is focused on environmental energy that is commonly present and is not dependent on fossil fuels or the like. As the environmental energy, power generation energy using sunlight or wind power is widely known, and an example of the environmental energy having an energy density similar to that of the above power generation energy includes vibration energy that is commonly present in surroundings.
A vibration power generator that generates power by using the vibration energy is developed, and an electret capable of holding electric charges semipermanently is widely used in the power generator. In the case where vibration power generation is performed by using the electret, it is required to maintain a gap between the electret and an electrode at a predetermined distance that allows excellent power generation efficiency. To cope with this, as described in Patent Document 1, Patent Document 1 discloses a technique in which, in a structure in which a substrate provided with the electret and a substrate provided with the electrode oppose each other, an adjustment member for adjusting the gap is disposed between a support member that supports one of the substrates and a support member that supports the other substrate.
In addition, as a configuration for maintaining the gap between the electret and the electrode, as described in Patent Document 2, there is disclosed a gap formation technique that is made less likely to be influenced by a thickness error of a substrate constituting a movable member by providing a first reference surface for mounting a fixed member and a second reference surface for positioning a slidable steel ball for supporting the movable member in a housing of a vibration power generator that generates power by relative movement of the movable member and the fixed member, fixing the fixed member via the first reference surface, and disposing the movable member via the second reference surface and the steel ball. Further, Patent Document 3 discloses a technique that suppresses narrowing of a gap between a movable member and a fixed member by using repulsion by electric charges.